The invention relates to an exhaust gas turbocharger for an internal combustion engine with a turbine housing having first and second spiral inlet channels for directing exhaust gas onto a turbine which is disposed in the turbine housing. The invention further relates to a motor vehicle with an internal combustion engine and such an exhaust gas turbocharger.
Due to the continuous tightening of the emission limit values, for example the NOx and soot emission values of motor vehicles, the demands of exhaust gas turbochargers or charged internal combustion engines also increase. Thus, there are increasing demands regarding the charge pressure provision with high exhaust gas recirculation rates (AGR rate) over medium to high load demand ranges of the internal combustion engine whereby the turbines of exhaust gas turbochargers are increasingly scaled down geometrically. In other words, the required high turbine performances of exhaust gas turbochargers are realized by an increase of the retention ability and a corresponding reduction of the intake ability of the turbines in cooperation with the respective internal combustion engine.
The performance of exhaust gas turbochargers is further affected by exhaust gas treatment systems arranged in the exhaust gas tract downstream of the turbine as for example soot filters, catalysts or SCR systems. These exhaust gas treatment systems lead to a pressure increase at an exhaust gas outlet of the exhaust gas turbocharger. This again causes a reduction of a turbine pressure gradient defining the performance of the exhaust gas turbocharger, wherein the turbine pressure gradient can be determined as the quotient of a gas pressure before the turbine wheel or an exhaust gas inlet of the turbine wheel housing and a gas pressure behind the turbine wheel or an exhaust gas outlet of the turbine housing. Also, due to this reason, the turbine size again has to be designed for lower values and thus lower efficiencies in order to be able to satisfy the performance demand of the compressor of the exhaust gas turbocharger.
A certain improvement is provided by exhaust gas turbochargers known in the state of the art, whose turbine housings comprise two spiral channels through which exhaust gas can be separately admitted to the turbine and which are respectively coupled to different exhaust gas lines of an exhaust gas tract of the internal combustion engine via annular inlet vane structures. The exhaust gas lines themselves are associated with different cylinders or cylinder groups of the internal combustion engine. One of the spiral channels thereby usually serves as a so-called lambda spiral which provides for the necessary air-fuel ratio via its exhaust gas retention ability. The other spiral channel serves in contrast as a so-called exhaust gas recirculation spiral (AGR spiral) and is responsible for the exhaust gas recirculation ability of the exhaust gas turbocharger.
With the design limit conditions of exhaust gas turbochargers, which are usually defined by a nominal operating point, a charge change aspect and a fuel consumption aspect of the internal combustion engine, particularly the lower load and speed range of internal combustion engines can often not be attended to in an optimum manner even with exhaust gas turbochargers with two spiral inlet channels. The flow cross-sectional areas of the spiral channels are in principle chosen to be as small as possible for this purpose, in order to be able to generate the necessary exhaust gas flow speeds.
It is a disadvantage of the known exhaust gas turbochargers that they have comparatively low efficiencies, so that also the requirement of an internal combustion engine provided with the exhaust gas turbocharger relatively high. This necessitates additional measures for an efficiency increase, whereby the manufacturing costs however also increase considerably.
It is thus the object of the present invention to which provides for an efficiency improvement with manufacturing costs as low as possible even with the highly transient requirements of internal combustion engine or motor vehicles.